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Re Capping - Printable Version

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Re Capping - Dick Finn - 08-03-2012

I've finished restoring the cabinet on my 37-660 and have made some progress recapping the chassis. The cabinet looks great after sitting in the regularily flooding basement in our old house. I've re glued the laminates and turned new feet. After stripping and re doing the laquer it looks like new.

I seem to have run into a sourcing problem and would appreciate some advice. The vendors on the list don't seem to cover a number of the capacitors the schematic says I need. Specifically:
110 pf
.1 mf (micro)
75 pf
1150 pf
.003 mf
250 pf
40pf

I've tried Digikey and they can help with all but the last two.

The schematic actually doesn't use the term pf. Instead they us micro micro (Which I read to be 10**-12 or a pico farad). I am curious as to why they just didn't call it a pf.

Also, the schematic does not specify and voltage requirements.

So, my question is, what voltage should I ask for and where can I get the capacitors.

Thanks,
Dick Finn

RE: Re Capping - Dave - 08-03-2012

http://www.justradios.com/cart.html

He's got all of the odd value caps. As far as voltage, most of what he carries is 630V, which is fine for most applications. Most schematics specify when a larger voltage rating is needed.

Dave

RE: Re Capping - DeckApe - 08-03-2012

I'll give a +1 to justradios.com. Good customer service and great selection.

RE: Re Capping - Dick Finn - 08-03-2012

Thanks guys, I just submitted an order for all my capacitors to Justradios. I'm looking forward to getting the order and finishing the re-capping. It will be exciting to start bringing up power and seeing if it still works.

RE: Re Capping - chucka - 08-04-2012

Rfinn5:

Is there a particular reason you're replacing the small value mica caps in the set?
Did they test bad or physically broken?
Normally these small caps are not an issue when restoring a set. They are usually found in the RF tuning section and unless I am having a tuning problem when aligning the front end, I leave them alone.

electrolytics & paper - always replace

mica & ceramic - almost never replace.

Unless you are really anal......


Chuck

RE: Re Capping - Phlogiston - 08-04-2012

Or they are in a 1950s IF can.

RE: Re Capping - marv - 08-04-2012

Hope you don't mind me jumping in here but if you are able could measure the primary resistance of your Range 1 RF coil? I have a 37-660 on my bench and believe my primary was bad. Schematic calls for 130 ohm and I measured less than 100. The "Philco" tape was across the outer windings under the wax (wave wound). BTW, the primary is cloth covered single strand #38 (I think). The cloth is missing in several layers. Multi strand is used for connection to the wafers.

marv

RE: Re Capping - Radioroslyn - 08-04-2012

Agree with Chuck on this one. Usually don't replace mica unless there's an alignment problem. The '50 IF xformers are called K Tran their 3/4x 3/4x 2 1/2" usually 455kc.
Terry

RE: Re Capping - codefox1 - 08-04-2012

I routinely recarbon as well anymore.

RE: Re Capping - Dick Finn - 08-04-2012

I was replacing the small mica caps because I'm a newbie at this and I read that the first thing you should do before powering up the set is to replace the capacitors. Not knowing better, I assumed htis meant all the capacitors. Thanks for the heads up, it looks like this will save me some trouble.

RE: Re Capping - chucka - 08-05-2012

There is one other exception to the mica cap rule. Any cap that looks like a mica but is marked "Micamold" replace as they are paper, just disguised.

Chuck

RE: Re Capping - exray - 08-05-2012

Well, sorta. Molded capacitors of larger values from most any manufacturer are likely to be paper. Be suspicious with anything higher than, say, .002 (2000pf). Any over .005 (5000pf) are almost always paper.

RE: Re Capping - Phlogiston - 08-05-2012

Amd don't forget to rerubber. If not wire, tuning cap mounts.

RE: Re Capping - Dick Finn - 08-05-2012

Great advice here and greatly appreciated. The last comment from Phlogiston caught my eye. Do you suggest using modern wire with modern insulation. Seems to me I read (many years ago) about a company that sold modern wire/insulation wrapped in cloth insulation for use on old electronics. Does any one know a supplier?

RE: Re Capping - Arran - 08-06-2012

I would just use vinyl covered wire in the appropriate colours, the closest modern equivailent to the rubber covered junk, 18 and 20 gauge preferably, solid or stranded depending on the application. You can buy repro cloth covered wire but why spend the extra when you don't have to.
On the subject of capacitors Radio Daze has a good selection, so does Bobs Antique radio supply, Mouser can supply most of the other stuff like resistors and precision ceramic and silver mica caps, and electrolytics. Leave the small mica caps alone unless there is a mystery problem that changing the usaul parts does not solve, unless it's one of those large wax dipped micas that Philco sometimes used.
Regards
Arran